The subject matter disclosed herein relates generally to heat recovery steam generators (HRSG) and, more specifically, to fluid flow into drums within the HRSG system.
An HRSG may be used as part of a combined cycle power plant, which includes both a gas turbine and a steam turbine. The gas turbine generates hot exhaust gases, which are used by the HRSG to generate steam to drive the steam turbine. The HRSG may include a number of drums to facilitate the heat exchange between the exhaust gas and water. Unfortunately, heating within each drum may create steam bubbles that can cause shrinking and swelling conditions to occur within the drum. Shrinking may be caused by an increase in the feed water supplied to the drum, which lowers the temperature within the drum and can cause steam bubbles to collapse. Collapsing bubbles in turn causes a drop in fluid level even though feed water is being added to the drum. Shrinking may also be caused when there is a sudden decrease in the amount of steam drawn from the drum which results in a sudden increase in pressure within the drum. Swelling conditions include a reversal of the shrinking conditions (i.e., a decrease in the feed water supply or a sudden increase in the amount of steam drawn from the drum) which results in a decrease in pressure within the drum. Swelling conditions may cause an increase in the number and size of the bubbles within the fluid in the drum, which increases the apparent fluid level. Shrinking and swelling conditions can potentially cause plant down time when fluid levels rise too high or drop too low.